Strike a tuning fork: it rings and gradually fades. Roughly the same happens to the edges of special quantum chains when they are suddenly "shaken": oscillations decay, and memory of the initial state disappears. But physicists have discovered that in some cases this ringing lasts surprisingly long.
The authors took a chain of alternating strong and weak bonds — a model known as the SSH chain . At its ends, special states emerge, like sentinels that keep energy from entering. The researchers abruptly changed the conditions (performed a quantum kick) and tracked the fate of these edge "guardians." It turned out that one thing decides everything: whether the new system has interactions between particles. Without interactions, memory of the initial configuration decays according to a strict law, like sound whose volume drops as time to the power of 3/2. But turn on interactions, and the picture changes.
Using computer simulations, the scientists showed that interactions significantly extend the life of edge memory. This is especially pronounced away from the special point where the system becomes symmetric (the so-called SU(2) point). A kind of collective protection mechanism emerges: although in such systems information usually gets "mixed up" and lost, here interactions, on the contrary, shield it. This is like an echo in the mountains that lasts longer not despite the rugged terrain but because of it.
The loop closes: a tuning fork fades quickly, but if you surround it with resonators, the sound persists. Similarly, a quantum edge — alone it is weak, but surrounded by interacting particles, its memory becomes nearly invulnerable.
The study used the SSH model — the very one that describes conductivity in polyacetylene, discovered back in the 1970s. Its authors received the Nobel Prize in Chemistry in 2000.
The idea of "protected memory" in quantum systems resembles the "ice palaces" in the series "Altered Carbon," where consciousness is stored in special substrates resistant to external influences.